RV Repair: Hooked battery up backwards, test light, auxillary

Question
Hi Shawn,
I recently bought a 1981 Winnebago Chieftian wiht a 454 engine, it runs good, or,it did until I screwed-up BIG TIME!!!
I was putting the engine battery back in (I took it out for the winter, the auxillary batteries were shot...froze up and swelled). It was a nice day,in the 60s, so, I thought I'd take it for a spin, that's when I hooked up the battery
backwrads. When I finished hooking it up I went inside to start the engine, but, noticed a smell...it wasn't the smell of burnt wires or burnt motor, it was the slight smell of an egg cooking.??? I didn't start the engine, but went back out to check the battery. That's when I reailzed what I had done. I corrected my mistake and tried starting the engine.
Nothing happened, no clicking ,no guage movement, nothing.
The battery is okay,I put it in my pickup and it cranked right up.
I do have lights,and, I did run a jump lead from the battery POS post to the sylanoid, the starter cranked the engine.
There is a little canister on the frame near the battery that the POS cable connects to before going to the starter,
is that a safty device to protect the electrical system??? Could that have been damaged?
I just don"t know where to start looking for damage.
Remember, I didn't start the engine, if that matters???
I gotta tell you I'm pretty sick about the thing.
If you could give me some kind of idea of the damage that may have occurred
and maybe how to go about checking these things out I'd greatly appreciate it.  

Answer
Hi Richard, Sorry it took so long to return this. I was out of town. The canister, I think is your Aux start solenoid. There are so many possibilities here. I would trace all the wiring with a test light. I would start at the starter, and work my way back to the ignition. Try to find were the power stops. There is no easy answer here. Sorry that happened. I've made some bone headed mistakes too. Good Luck.